It's an easy drive from Glenns Falls to Clairemont, NH -- a straight shot on US 4. I've driven a large part of that road, and it's easy traffic on an easy road.
A very large portion of the East Coast Alliance folk drive two to three hours to get to a game. When the Caldaria game changing ownership, I would drive three hours west to PA from Central Connecticut, and before that (before Caldaria moved to Easter CT) I would drive over two hours to Northcentral MA.
So, whether you go to the Crossroads (NY) game and/or the Deadlands (NH) game, it is definitely worth the drive -- the people who play there and the people who manage there make for some great LARPing. They definitely welcome new folks and will make you feel at home in no time.
I don't how direct or how frequent the public transportation is to Clairemont, but as it is a straight shot along US 4, I would expect that there is at least one bus line that makes the trip on a several times a day basis - go down to the bus station in Glenns Falls and ask -- or look it up online.
As far as a bus to Crossroads -- you might have to make a change in Albany, but I am sure that you can find public transport south to where you can get a ride to game.